In general, a battery indicates both non-rechargeable primary cells and rechargeable secondary cells (also called rechargeable batteries). Batteries are classified on the basis of the underlying chemical redox reaction, the materials used, the electrical values (for example voltage or capacitance) or the geometric or structural design. Examples include alkaline-manganese batteries, zinc-carbon batteries or lithium batteries. A distinction is also drawn between winding cells and stacked batteries in batteries, depending on their inner construction. In the case of a winding cell, the electrode and separator layers which are arranged one above the other are wound up in a spiral manner and installed, for example, in a round battery with a cylindrical housing. In the case of a stacked battery however, a plurality of electrode and separator layers are alternately stacked one above the other.
FIG. 1 shows, by way of example, a stacked battery. As shown in FIG. 1, an anode 10 and a cathode 20 are alternately arranged in the battery, wherein a separator 30 is arranged between the anode 10 and the cathode 20 in each case in order to physically and electrically separate the two electrodes. However, the separator 30 has to be permeable to ions which cause the conversion of the stored chemical energy into electrical energy. Microporous plastics or nonwovens which are composed of glass fiber or polyethylene are usually used for separators 30. The anodes 10 are connected to one another in their arrester regions 40, as are the cathodes 20, with the result that all electrodes of the same kind in a battery are interconnected. A connection lug 50 (see FIG. 2B) for the cathodes 20 and the anodes 10 is mounted in the arrester regions 40 in each case, said connection lug being connected to a corresponding outer voltage pole of the battery.
FIG. 2A shows a plan view of a cathode 20 with an arrester region 40. The cathodes 20 are connected to one another in the arrester regions 40 of the cathodes 20 which are arranged one above the other. As shown in FIG. 2B, the connection lug 50 is mounted on the arrester regions 40 which are connected to one another, said connection lug being in contact with the negative pole of the battery after the battery is assembled.
Battery electrodes are usually prefabricated as bulk or rolled material from which a desired electrode shape is cut out during production of a battery. As shown in FIG. 3, the electrode material comprises a collector substrate 60 which is provided with a coating film 70. In this case, the electrode material has one or more uncoated arrester regions 40 which are required later in the assembled state in order to discharge voltage or current to the outside. A plurality of electrodes of the same kind are connected to one another at, and a metal connection lug 50 is mounted on, the arrester regions 40. When the collector substrate 60 is coated on both sides, arrester regions 40 are therefore also formed on both sides. In this case, the arrester regions do not necessarily have to be formed opposite one another but can be offset in relation to one another, as shown in FIG. 3.
FIGS. 4A and 4B show methods for producing an electrode material by means of a slot die system 300. An ink-like coating film 70 is applied on the strip-like collector substrate 60. This application process can be performed either by discontinuous, intermittent coating, wherein an uncoated arrester region 40 is formed by regular interruption in the coating as shown in FIG. 4A, or by continuous coating, as shown in FIG. 4B. However, forming relatively complex arrester regions using these methods is very complicated. Therefore, masking steps are occasionally used. As an alternative, arrester regions 40 can be exposed on a collector substrate 60 by brushing or similar methods.
After coating, the electrode material is calendered in order to compress the coating film and to eliminate cavities which are produced when the coating film 70 is drying. The finished electrode material can then be rolled up and stored until further processing. A desired shape, which is different depending on the type of battery or shape of the battery, is cut out or stamped out of the electrode material in order to produce a battery. When the battery electrode is cut out, it is additionally necessary to ensure that an arrester region 40 must be present. An example of a rectangular electrode shape with an arrester region 40 is shown in FIG. 2A.
FIG. 5 shows a flowchart which is used to illustrate the production process of a battery, for example a winding cell or a stacked battery. First, the collector substrate 60 is coated with the coating film 70, for example using an intermittent method (S10), wherein a plurality of uncoated arrester regions 40 are formed by interruption or discontinuation when applying the ink-like coating. The electrode material is then calendered (S20). A desired electrode shape can then be cut out or stamped out of the electrode material (S30), wherein the stamped-out shape has to have an arrester region 40. These steps are performed both when producing the anode 10 and when producing the cathode 20. Next, the stamped-out electrodes are arranged one above the other (S40) such that an anode 10 and a cathode 20 with a separator 30 therebetween are arranged alternately in succession (see FIG. 1). In this case, the arrester regions 40 of the cathodes 20 and the arrester regions 40 of the anodes 10 are in each case arranged one above the other and are connected to one another. A connection lug 50 is then mounted on said arrester regions (S50). In this case, the number of anodes 10 and cathodes 20 which are arranged one above the other can vary depending on the type and property of the battery. After the electrode arrangement is complete, the electrode arrangement is inserted into a housing and the connection lugs 50 are connected to the outer voltage poles of the housing (S60). In the case of a winding cell, the electrode arrangement is also wound up in a spiral manner and inserted into the housing in this state. After the electrolyte is introduced (S70), the cell is then sealed (S80) and finally formed (S90).
However, the following problems are encountered in the conventional methods for producing battery electrodes. For example, the production of uncoated arrester regions by masking steps or brushing away the coating is very complex and expensive. In the alternative production method by intermittent or continuous coating with the aid of a slot die system however, the possible shapes and arrangements of the arrester regions on the electrode material are greatly restricted. In view of the various fields of use of batteries, in particular in design products such as mobile telephones, laptops or cars, however, flexibility in respect of the configuration of the battery electrodes is increasingly required. In this case, the trend toward relatively small devices poses a particular challenge to battery production. Firstly, batteries with relatively small dimensions therefore have to be developed, and secondly complex shapes are often required in order to make the most efficient use of the interior of a device as possible. Furthermore, it is difficult to produce regular and clean edge regions between the coating region and the arrester region in the case of an intermittent coating method.
Furthermore, it is difficult and expensive to realize a variety of shapes of the electrodes with the conventional methods. For reasons of cost, a rolled material is usually used as the electrode material, possible positions of the uncoated arrester region 40 in relation to the coating film 70 being fixedly defined in said rolled material. As a result however, the degree of freedom of design for the electrode shape is severely restricted because each electrode has to have an arrester region 40. In addition, a large amount of excess electrode material which has to be disposed of is produced when the desired electrode shape together with the arrester region 40 is cut out. If, for example, small electrodes are cut out such that they contain an arrester region 40, regions of the coated substrate which is situated between successive arrester regions 40 can no longer be used when there is a large distance between said successive arrester regions. As a result, material consumption is increased and the production method is more expensive. Furthermore, a dedicated stamping die for stamping out the desired shape has to be created for each desired electrode shape. However, these stamping dies are very expensive on account of the high demands made on cutting quality.
In the conventional production methods, the arrester region 40 is formed beforehand by a coated electrode region in order to mount the connection lug 50 on said arrester region and to connect electrodes of the same kind to one another. However, this leads to unutilized space in the battery which is not filled with active electrode material. As a result, the size of the battery is unnecessarily increased and/or an outer shape of the battery is fixed.
Furthermore, the arrester regions 40 can be easily contaminated in the conventional production methods or else during storage. Impurities can reach the arrester regions 40 in the case of a calendering process in particular. This has an adverse effect on the quality of an electrical contact between electrodes of the same kind and between the electrodes and an associated connection lug 50. Since the arrester regions 40 are additionally formed before the calendering process during production of the electrode material, calendering is made more difficult on account of the non-uniformly thick structure. In addition, the arrester region 40 which is formed by conventional methods may be poorly defined, wherein particularly an edge region of the arrester region 40 can be formed in an inaccurate and non-uniform manner.